An abrupt southerly wind change, often producing strong and squally winds and sometimes accompanied by thunderstorms and a sharp drop in temperature. These strike Sydney mainly during the summer months.

5 January 2005

worrying about the Old Peak

It may not happen anytime soon, but the Cumbre Vieja volcano in the Canary Islands is bound to erupt again - and when it does, it may well set in motion a tsunami wave more massive than any in recorded history. According to a new model by Simon Day of University College London and Steven Ward of the University of California, this mega-tsunami, which they describe in the September 2001 issue of Geophysical Research Letters, would rouse waves 100 meters high along the West Saharan shore, seas more than 40 meters high on the north coast of Brazil, and water walls towering 50 meters in the air off the coast of Florida and in the Caribbean. Britain, Spain, Portugal and France would also face sizeable waves.

Day and his colleagues predicted earlier that a future eruption of Cumbre Vieja would most likely prompt a serious landslide on the volcano's western side. They guessed that a chunk of rock twice the volume of the Isle of Man might break off, rush into the sea and create a debris avalanche deposit extending as far as 60 kilometers from the island. The new model adds to this picture, forecasting that Cumbre Vieja's collapse would send up a dome of water 900 meters high and tens of kilometers wide. As that dome collapsed and rebounded, giant waves would form and build, fueled by what is known as a tsunami wave train, itself created as the landslide sped away from the island underwater. In 10 minutes, such a tsunami would travel almost 250 kilometers.

A wall of water up to 55 yards high crashing into the Atlantic seaboard of the United States, flattening everything in its path -- not a Hollywood movie but a dire prophecy by some British and U.S. academics.

As the international community struggles to aid victims of last month's devastating tsunami in southern Asia, scientists warn an eruption of a volcano in Spain's Canary Islands could unleash a "mega-tsunami" larger than any in recorded history.

According to their controversial study, an explosion of the Cumbre Vieja volcano on the island of La Palma could send a chunk of rock twice the size of the Isle of Wight into the Atlantic at up to 220 miles an hour.

Many experts believe the risk of "mega-tsunamis" from such a massive landslide on La Palma has been hugely overstated.

But in the study's scenario, energy released would equal the electricity consumption of the United States for six months, sending gigantic tidal waves across the Atlantic at the speed of a jet plane.

It's now obvious a tsunami warning system will be set up in the Indian Ocean. One hopes we don't end up having the same debate some time about why no-one thought to set up an Atlantic Ocean system. Or why no-one thought to monitor Cumbre Vieja.